CODEWITHSUNDEEP
rubyif-statementconditional-statementsmultiple-conditions
Jeffrey Green
Jeffrey Green

Reputation: 173

Ruby - Using multiple conditions on a single line

So, I'm running into this issue wherein I want to have three conditions be checked before the routine continues, but it keeps throwing up syntax errors saying it didn't expect the multiple conditions. Now, I know I've seen other people use lines such as:

if x > 100 && x % 2 == 1
    #Do something
end

But, for whatever reason, this line: 

if (letters.eql? letters.upcase && dash.eql? '-' && numbers.to_i.to_s.eql? numbers)

is throwing up tons of errors. Is it something to do with '.eql?' or is it something extraneous about Ruby that I haven't encountered yet?

Here's the rest of the code for reference:

print "Enter license plate: ";
input = gets.strip;
if input.length == 8
    letters = input[0,2];
    dash = input[3];
    numbers = input[4,7];
    if (letters.eql? letters.upcase && dash.eql? '-' && numbers.to_i.to_s.eql? numbers)
        puts "#{input} is a valid license plate."
    else
        print "All valid license plates are three (3) uppercase letters, followed by a dash (-), followed by four (4) digits";
    end
else
    print "All valid license plates are 8 characters long.";
end

Also, these are the errors:

LicensePlate.rb:7: syntax error, unexpected tSTRING_BEG, expecting ')'
...? letters.upcase && dash.eql? '-' && numbers.to_i.to_s.eql? ...
...                               ^
LicensePlate.rb:7: syntax error, unexpected tIDENTIFIER, expecting ')'
... numbers.to_i.to_s.eql? numbers)
...

Upvotes: 11

Views: 48061

Answers (4)

Stefan
Stefan

Reputation: 114138

In addition to the other answers - consider using a regular expression to check the format:

print "Enter license plate: "
input = gets.chomp
if input.length != 8
  puts "All valid license plates are 8 characters long."
elsif input !~ /^[A-Z]{3}-\d{4}$/
  print "All valid license plates are three (3) uppercase letters, followed by a dash (-), followed by four (4) digits"
else
  puts "#{input} is a valid license plate."
end

Upvotes: 1

Ohad Dahan
Ohad Dahan

Reputation: 351

This also works:

letters.eql? letters.upcase and dash.eql? '-' and numbers.to_i.to_s.eql? numbers

I believe this is due to operator precedence since this also works:

(letters.eql? letters.upcase) && (dash.eql? '-') && (numbers.to_i.to_s.eql? numbers)

Ruby seem to try and evaluate your condition prematurely.

EDIT: Just saw that Lurker was mentioning precedence previously.

Upvotes: 4

Ryan Rebo
Ryan Rebo

Reputation: 1318

This should do it:

if letters.eql?(letters.upcase) && dash.eql?('-') && numbers.to_i.to_s.eql?(numbers)

You can still wrap the entire conditional in parenthesis if you would like, but with Ruby (unlike JavaScript), you don't need to.

Upvotes: 10

Rob Mulholand
Rob Mulholand

Reputation: 899

Think you're just missing some parens - try this:

if (letters.eql?(letters.upcase) && dash.eql?('-') && numbers.to_i.to_s.eql?(numbers))

Upvotes: 6

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